Feed unit, electronic unit, and feed system

ABSTRACT

A power receiving circuit, a power transmitting circuit, an apparatus, and a feed system are disclosed. The power receiving circuit receives power in a noncontact manner, and includes an LC parallel resonant circuit and a reactance element that is electrically connected in series to the LC parallel resonant circuit. The reactive element may be a capacitive or inductive element. In effect, a coil or capacitor in the LC parallel resonant circuit and the reactance element define another LC resonant circuit, namely, an LC series resonant circuit. The power transmitting circuit transmits power in a noncontact manner, and in one example, may also include a similar configuration.

TECHNICAL FIELD

The present disclosure relates to a feed system that supplies(transmits) power to a target unit, such as an electronic unit, in anoncontact manner, and a feed unit and the electronic unit used for thefeed system.

BACKGROUND ART

Recently, a feed system, such as a noncontact feed system and a wirelesscharging system, has been noticed, which supplies (transmits) power toconsumer electronics (CE) devices such as a mobile phone and a portablemusic player in a noncontact manner. This enables charge of anelectronic unit (secondary unit) only by placing the electronic unit ona charging tray (primary unit) instead of inserting or connecting aconnector of a power supply unit, such as an AC adaptor, into or to theelectronic unit. Specifically, this eliminates terminal connectionbetween the electronic unit and the charging tray.

An electromagnetic-induction-type power supply is generally known assuch noncontact power supply. In addition, a noncontact feed system hasbeen recently noticed, which utilizes a method, called magneticresonance method, based on an electromagnetic resonance phenomenon. Sucha noncontact feed system is, for example, disclosed in NTL 1.

CITATION LIST Non-Patent Literature

-   [NTL 1] K. Kanai and others, “Solution to Voltage Ratio Problem on    the Moving Pick-up Type Contactless Power Transfer System Using    Series and Parallel Resonant Capacitors”, Proceeding of Technical    Meeting on Semiconductor Power Conversion, SPC-10-021 (Jan. 29,    2010)

SUMMARY OF INVENTION

In the noncontact feed system as described above, it would be useful toimprove transmission characteristics, for example, transmissionefficiency, for charge of a plurality of feeding target units (so-called1:N charge), for example. In addition, it would be useful to improve thetransmission characteristics in a simple configuration withoutincreasing the number of components, for example. It is thereforedesirable to propose a method that enables an improvement intransmission characteristics in a simple configuration during powertransmission with a magnetic field (noncontact feeding).

It is desirable to provide a feed unit, a target unit, and a feedsystem, which enable an improvement in transmission characteristics in asimple configuration during power transmission with a magnetic field.Disclosed herein are one or more inventions pertaining to feed units,target units, and feed systems.

According to one embodiment, a power receiving circuit that receivespower in a noncontact manner is provided. In particular, the powerreceiving circuit includes an LC parallel resonant circuit and areactance element electrically connected in series to the LC parallelresonant circuit. The reactance element may be a capacitive element oran inductive element. Further, a coil or a capacitor in the LC parallelresonant circuit and the reactance element define an LC series resonantcircuit.

According to another embodiment, a power transmitting circuit thattransmits power in a noncontact manner is provided. In particular, thepower transmitting circuit includes an LC parallel resonant circuit anda reactance element electrically connected in series to the LC parallelresonant circuit. The reactance element may be a capacitive element oran inductive element. Further, a coil or a capacitor in the LC parallelresonant circuit and the reactance element define an LC series resonantcircuit.

In other embodiments, an apparatus and a feed system are provided. Moreparticularly, the apparatus, such as an electronic unit, includes apower receiving section that includes an LC parallel circuit and areactance element electrically connected in series to the LC parallelresonant circuit. The power receiving section receives power in anoncontact manner. In this regard, power may be transmitted with amagnetic field and received via a coil (a power receiving coil) in theLC parallel resonant circuit. Further, the coil or a capacitor in the LCparallel resonant circuit and the reactance element define an LC seriesresonant circuit. The reactance element may be a capacitive element oran inductive element.

A feed system according to one embodiment includes a feed unit and oneor more target units receiving power transmitted by the feed unit. Eachof the one or more target units includes a power receiving section thatreceives power from the feed unit in a noncontact manner. The powerreceiving section has an LC parallel resonant circuit and a reactanceelement electrically connected in series to the LC parallel resonantcircuit. The reactance element may be a capacitive or inductive element.Further, a coil or a capacitor in the LC parallel resonant circuit andthe reactance element define an LC series resonant circuit.

In another embodiment, a feed system including a feed unit and one ormore target units (e.g., electronic units) receiving power transmittedby the feed unit is provided. The feed unit includes a powertransmission section including an LC parallel resonant circuit and areactance element electrically connected in series to the LC parallelresonant circuit. The reactance element may be a capacitive or inductiveelement. The power transmission section transmits power to each of theone or more target units in a noncontact manner. In this regard, powermay be transmitted with a magnetic field via a coil (a powertransmission coil) in the LC parallel resonant circuit. Further, a coilor a capacitor in the LC parallel resonant circuit and the reactanceelement define an LC series resonant circuit.

A feed system according to an embodiment of the disclosure may includeone or more electronic units, and a feed unit transmitting power to theone or more electronic units. The feed unit may include a powertransmission section including a power transmission coil for powertransmission and a first capacitor, and the electronic units may eachinclude a power receiving section including a power receiving coilreceiving power transmitted through power transmission and a secondcapacitor. In one or both of the power transmission section and thepower receiving section, the power transmission coil or the powerreceiving coil and the first or second capacitor are connected inparallel to each other and thus define a parallel circuit, and areactance element is provided in series connection to the parallelcircuit.

In various disclosed embodiments, a coil and a capacitor in the LCparallel resonant circuit are connected in parallel to each other, andthus form a parallel circuit, and the reactance element is connected inseries to the parallel circuit. As a result, during power transmissionwith a magnetic field, the parallel circuit on a receive side and/ortransmit side performs an LC parallel resonance operation, and the coilor the capacitor in the parallel circuit and the reactance elementdefine a resonant circuit that performs an LC resonance operation (LCseries resonance operation).

As a result, for example, even if power is transmitted to a plurality oftarget units, such as a plurality of electronic units, transmissioncharacteristics including transmission efficiency are improved withoutincreasing components. Consequently, the transmission characteristicsare improved in a simple configuration during power transmission with amagnetic field.

It is to be understood that both the foregoing general description andthe following detailed description are provided for purpose ofillustration only, and not by way of limitation.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments and,together with the specification, serve to explain the principles of thetechnology.

FIG. 1 is a perspective view illustrating an example appearanceconfiguration of a feed system according to a first embodiment of thedisclosure.

FIG. 2 is a block diagram illustrating an example detailed configurationof the feed system shown in FIG. 1.

FIG. 3 is a circuit diagram illustrating an example detailedconfiguration of each of a power transmission section and a powerreceiving section shown in FIG. 2.

FIG. 4 is a circuit diagram illustrating an example configuration ofeach of a power transmission section and a power receiving section of afeed system according to a comparative example 1-1.

FIGS. 5A and 5B are characteristic diagrams illustrating exampletransmission characteristics according to the comparative example 1-1.

FIG. 6 is a circuit diagram illustrating an example configuration ofeach of a power transmission section and a power receiving section of afeed system according to a comparative example 1-2.

FIGS. 7A and 7B are characteristic diagrams illustrating exampletransmission characteristics according to the comparative example 1-2.

FIG. 8 is a circuit diagram illustrating an example configuration ofeach of a power transmission section and a power receiving section of afeed system according to a comparative example 2-1.

FIG. 9 is a characteristic diagram illustrating example transmissioncharacteristics according to the comparative example 2-1.

FIG. 10 is a circuit diagram illustrating an example configuration ofeach of a power transmission section and a power receiving section of afeed system according to a comparative example 2-2.

FIG. 11 is a characteristic diagram illustrating example transmissioncharacteristics according to the comparative example 2-2.

FIGS. 12A and 12B are characteristic diagrams illustrating exampletransmission characteristics according to Example 1 of the firstembodiment.

FIG. 13 is a circuit diagram illustrating an example configuration ofeach of a power transmission section and a power receiving section of afeed system according to a second embodiment.

FIG. 14 is a characteristic diagram illustrating example transmissioncharacteristics according to Example 2 of the second embodiment.

FIGS. 15A and 15B are circuit diagrams illustrating an exampleconfiguration of a power transmission section of a feed system accordingto a third embodiment.

FIG. 16 is a block diagram illustrating an example configuration of afeed system according to a fourth embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the disclosure will be described in detailwith reference to the accompanying drawings. It is to be noted thatdescription is made in the following order.

1. First Embodiment (example of a secondary unit where a capacitiveelement is connected in series to an LC parallel resonant circuit)

2. Second Embodiment (example of a secondary unit where an inductiveelement is connected in series to an LC parallel resonant circuit)

3. Third Embodiment (example of a primary unit where a capacitive orinductive element is connected in series to an LC parallel resonantcircuit)

4. Fourth Embodiment (example of a combination of the primary andsecondary units in the first to third embodiments)

5. Modifications

First Embodiment Overall Configuration of Feed System 4

FIG. 1 illustrates an example appearance configuration of a feed system(a feed system 4) according to a first embodiment of the disclosure.FIG. 2 illustrates an example block configuration of the feed system 4.The feed system 4 is an example of a noncontact feed system thatperforms power transmission (power supply, or feeding) in a noncontactmanner with a magnetic field (e.g., with magnetic resonance,electromagnetic induction, and others). The feed system 4 includes afeed unit 1 (primary unit) and one or more electronic units, here, twoelectronic units 2A and 2B (secondary units) as feeding target units.

In the feed system 4, for example, as shown in FIG. 1, when theelectronic units 2A and 2B are placed on (or set in proximity to) a feedface (power transmission face) S1 of the feed unit 1, the feed unit 1transmits power to the electronic units 2A and 2B. Here, the feed unit 1has a mat-like (tray-like) shape, in which an area of the feed face S1is larger than an area of the plurality of electronic units 2A and 2B asa feeding target in consideration of a case where power is transmittedto the electronic units 2A and 2B simultaneously or in a time-divisionmanner (sequentially).

(Feed Unit 1)

As described above, the feed unit 1, as a charging tray, transmits powerto the electronic units 2A and 2B with a magnetic field. For example, asshown in FIG. 2, the feed unit 1 includes a power transmission sub-unit11 including a power transmission section 110, a high-frequency powergeneration circuit (an AC signal generation circuit) 111, and animpedance matching circuit 112.

The power transmission section 110 includes a power transmission coil(primary coil) L1 described below and a capacitor C1 (resonancecapacitor, or a first capacitor). The power transmission section 110includes the power transmission coil L1 and the capacitor C1 and thusperforms power transmission with a magnetic field to the electronicunits 2A and 2B (more particularly, to a power receiving section 210described below). In detail, the power transmission section 110 has afunction of emitting a magnetic field (magnetic fluxes) from the feedface S1 to the electronic units 2A and 2B. It is to be noted that adetailed configuration of the power transmission section 110 isdescribed below (FIG. 3).

The high-frequency power generation circuit 111 is a circuit generatinga predetermined high-frequency power (AC signal) for power transmissionwith power supplied from an external power supply source 9 of the feedunit 1, for example. Such a high-frequency power generation circuit 111includes, for example, a switching amplifier.

The impedance matching circuit 112 is a circuit for impedance matchingduring power transmission. The efficiency (transmission efficiency) isimproved through such impedance matching during power transmission. Itis to be noted that the impedance matching circuit 112 may be omitteddepending on a configuration of each of the power transmission coil L1,a power receiving coil L2 described below, and a resonance capacitor.

(Electronic Units 2A and 2B)

The electronic units 2A and 2B include, for example, stationaryelectronic units, such as a television receiver, or portable electronicunits, each having a rechargeable battery, Examples of a portable unitinclude a mobile phone and a digital camera. For example, as shown inFIG. 2, the electronic units 2A and 2B may each include a powerreceiving sub-unit 21, and a load 22 performing a predeterminedoperation (an operation allowing a function of the electronic unit to beexhibited) based on the power supplied from the power receiving sub-unit21. The power receiving sub-unit 21 includes a power receiving section210, an impedance matching circuit 212, a rectifier circuit 213, avoltage stabilization circuit 214, and a battery 215.

The power receiving section 210 includes the power receiving coil(secondary coil) L2 described below and a capacitor C2 p (resonancecapacitor, or a second capacitor). The power receiving section 210includes the power receiving coil L2 and the capacitor C2 p and thus hasa function of receiving power transmitted from the power transmissionsection 110 in the feed unit 1. A detailed configuration of the powerreceiving section 210 is also described below (FIG. 3).

The impedance matching circuit 212 is a circuit for impedance matchingduring power transmission as in the impedance matching circuit 112. Itis to be noted that the impedance matching circuit 212 may also beomitted depending on the configuration of each of the power transmissioncoil L1, the power receiving coil L2 described below, and the resonancecapacitor.

The rectifier circuit 213 is a circuit that rectifies power (AC power)supplied from the power receiving section 210 to generate DC power.

The voltage stabilization circuit 214 performs a predetermined voltagestabilization operation based on the DC power supplied from therectifier circuit 213 to charge the battery 215 and a battery (notshown) in the load 22.

The battery 215, which is charged by the voltage stabilization circuit214 and thus stores power, includes, for example, a rechargeable battery(secondary battery) such as a lithium-ion battery. It is to be notedthat in the case where only the battery in the load 22 is used, or thelike, the battery 215 may be omitted.

[Detailed Configurations of Power Transmission Section 110 and PowerReceiving Section 210] (Power Transmission Section 110)

FIG. 3 is a circuit diagram illustrating an example detailedconfiguration of each of the power transmission section 110 and thepower receiving section 210. It is to be noted that an impedance Z1shown in the drawing indicates an impedance as seen from the powertransmission section 110 to the high-frequency power generation circuit111, and an impedance Z2 and an impedance Z3 indicate impedances as seenfrom the power receiving section 210 in the electronic units 2A and 2B,respectively, to the rectifier circuit 213.

The power transmission section 110 includes the power transmission coilL1 for power transmission (generation of magnetic fluxes) with amagnetic field, and the capacitor C1 that together with the powertransmission coil L1 define an LC resonant circuit (LC series resonantcircuit). The capacitor C1 is electrically connected in series to thepower transmission coil L1. Specifically, a first end of the capacitorC1 is connected to a first end of a block of the impedance Z1, a secondend of the capacitor C1 is connected to a first end of the powertransmission coil L1, and a second end of the power transmission coil L1is grounded. It is to be noted that a second end of the block of theimpedance Z1 is also grounded.

The LC series resonant circuit including the power transmission coil L1and the capacitor C1 performs an LC resonance operation at a resonancefrequency, f_(res)=1/{2π×√(L1×C1)}, which is substantially the same asor close to a frequency of the high-frequency power (AC signal)generated by the high-frequency power generation circuit 111.

(Power Receiving Section 210)

The power receiving section 210 includes the power receiving coil L2receiving power (from the magnetic fluxes) transmitted from the powertransmission section 110, the capacitor C2 p that together with thepower receiving coil L2 define an LC resonant circuit (LC parallelresonant circuit), and a capacitor C2 s as a capacitive reactanceelement (capacitive element). The capacitor C2 p is electricallyconnected in parallel to the power receiving coil L2, and the capacitorC2 s is electrically connected in series to the power receiving coil L2,or to the LC parallel resonant circuit. Specifically, a first end of thecapacitor C2 p is connected to a first end of the power receiving coilL2 and a first end of the capacitor C2 s, and a second end of thecapacitor C2 s is connected to a first end of a block of the impedanceZ2 or Z3. Second ends of the power receiving coil L2, the capacitor C2p, and the blocks of the impedance Z2 and the impedance Z3 are grounded.

In the embodiment, the power receiving coil L2 and the capacitor C2 pdefine the LC parallel resonant circuit, and the power receiving coil L2in the LC parallel resonant circuit and the capacitor C2 s define the LCresonant circuit (the LC series resonant circuit). In addition, asdescribed in detail below, these two LC resonant circuits (the LCparallel resonant circuit and the LC series resonant circuit) perform LCresonance operations at the resonance frequency, f_(res), which issubstantially the same as or close to the frequency of thehigh-frequency power (AC signal) generated by the high-frequency powergeneration circuit 111. Specifically, the LC resonant circuit (LC seriesresonant circuit) defined by the power transmission coil L1 and thecapacitor C1 in the power transmission section 110 and each LC resonantcircuit defined by the power receiving coil L2 and each of thecapacitors C2 p and C2 s in the power receiving section 210 perform theLC resonance operations at substantially the same frequency, f_(res).

[Function and Effect of Feed System 4] (1. Outline of Overall Operation)

In the feed system 4, the feed unit 1 includes the high-frequency powergeneration circuit 111 that supplies the predetermined high-frequencypower (AC signal) for power transmission to the power transmission coilL1 and the capacitor C1, or to the LC series resonant circuit, in thepower transmission section 110. As a result, the power transmission coilL1 in the power transmission section 110 generates a magnetic field(magnetic fluxes). During this, the electronic units 2A and 2B asfeeding target units (charging target units) are placed on (or set inproximity to) the top (the feed face S1) of the feed unit 1, and thusthe power transmission coil L1 in the feed unit 1 is in proximity to thepower receiving coil L2 in each of the electronic units 2A and 2B in thevicinity of the feed face S1.

In this way, the power receiving coil L2 is disposed in proximity to thepower transmission coil L1 generating the magnetic field (magneticfluxes). Thus, an electromotive force is induced in the power receivingcoil L2 by the magnetic fluxes generated from the power transmissioncoil L1. In other words, a magnetic field is generated byelectromagnetic induction or magnetic resonance in linkage to each ofthe power transmission coil L1 and the power receiving coil L2.Consequently, power is transmitted from the power transmission coil L1(a primary side, namely, the feed unit 1 or the power transmissionsection 110) to the power receiving coil L2 (a secondary side, namely,the electronic units 2A and 2B or the power receiving section 210) (seepower P1, P1 a, and P1 b shown in FIGS. 2 and 3). During this, the powertransmission coil L1 and the capacitor C1 perform the LC resonanceoperation in the feed unit 1, and the power receiving coil L2 and thecapacitors C2 p and C2 s perform the LC resonance operation in theelectronic units 2A and 2B.

In the electronic units 2A and 2B, the AC power received by the powerreceiving coil L2 is thus supplied to the rectifier circuit 213 and thevoltage stabilization circuit 214 for the following charging operation.Specifically, the AC power is converted to a predetermined DC power bythe rectifier circuit 213, and then the voltage stabilization circuit214 performs a voltage stabilization operation based on the DC power forcharge of the battery 215 or the battery (not shown) in the load 22. Inthis way, a charging operation is performed in the electronic units 2Aand 2B based on the power received by the power receiving section 210.

Specifically, in the embodiment, the electronic units 2A and 2B areplaced on (or set in proximity to) the feed face S1 of the feed unit 1,and thereby are readily charged without terminal connection to an ACadaptor, for example (are readily supplied with power in a noncontactmanner). This reduces a burden on a user.

(Function of Power Receiving Section 210)

The function of the power receiving section 210 in the embodiment is nowdescribed in detail in comparison with comparative examples (comparativeexamples 1-1, 1-2, 2-1, and 2-2).

Comparative Example 1-1

FIG. 4 illustrates a circuit configuration of each of a feed section(power transmission section) 110 and a power receiving section 100 in afeed system (a feed system 104A) according to a comparative example 1-1.In the comparative example 1-1, the feed system 104A includes one feedunit 1A having a power transmission section 110A, and one electronicunit 102 having a power receiving section. The electronic unit 102 has aconfiguration similar to that of the electronic units 2A and 2B in theembodiment except that the power receiving section 100 is provided inplace of the power receiving section 210.

The power receiving section 100 includes a power receiving coil L2 and acapacitor C2 as a resonance capacitor. The power receiving coil L2 andthe capacitor C2 are connected in parallel to each other and thus definean LC parallel resonant circuit. Specifically, the power receivingsection 100 is different in a configuration from the power receivingsection 210 in that the capacitor C2 is provided in place of thecapacitor C2 p, while the capacitor C2 s is not provided (is omitted).

The feed system 104A including the power receiving section 100 havingsuch a configuration shows transmission characteristics, for example, asshown in FIGS. 5A and 5B during power transmission with a magnetic fieldas shown by an arrow P101 in FIG. 4, for example. Specifically, forexample, the transmission characteristic (frequency dependence of inputimpedance Zin1 of the feed unit 1) illustrated in FIG. 5A shows that theinput impedance Zin1 is minimized at a frequency in the vicinity of theresonance frequency f_(res) of 120 kHz. In addition, for example, thetransmission characteristic (frequency dependence of an S parameter S21for transmission efficiency between the feed unit 1 (primary side) andthe electronic unit 102 (secondary side)) illustrated in FIG. 5B showsthat the S parameter S21 is maximized at a frequency in the vicinity ofthe resonance frequency f_(res) of 120 kHz. Specifically, in thecomparative example 1-1, desirable power transmission (powertransmission at a high transmission efficiency) is achieved in thevicinity of the frequency (the resonance frequency f_(res) of 120 kHz)used for power transmission.

It is to be noted that the transmission characteristics shown in FIGS.5A and 5B are obtained by simulation under an example condition ofZ1=10Ω, Z2=10Ω, L1=393 μH, C1=4.5 nF, L2=2.5 μH, and C2=703 nF. Forexample, a value 0.1 calculated from a measured value is used as acoupling coefficient K for the simulation herein, and in othercomparative examples and Examples described below.

Comparative Example 1-2

However, for example, if a plurality of feeding target units (here, twoelectronic units 102A and 102B) each having the power receiving section100 are provided as in a feed system (a feed system 104B) according tothe comparative example 1-2 shown in FIG. 6, the following difficultymay occur.

Specifically, for example, as in the transmission characteristics asshown in FIGS. 7A and 7B, the transmission characteristics may abruptlydegrade at a frequency in the vicinity of the resonance frequencyf_(res) of 120 kHz during power transmission with a magnetic field asshown by arrows P101 a and P101 b in FIG. 6. Such a phenomenon tends tooccur in the case where a difference in a load is large between theplurality of feeding target units, for example, in the case where oneelectronic unit 102A has an impedance Z2 of 300Ω (light load), and theother electronic unit 102B has an impedance Z3 of 10Ω (heavy load). Indetail, in the transmission characteristic shown in FIG. 7A, the inputimpedance Zin1 abruptly increases at a frequency in the vicinity of theresonance frequency f_(res) of 120 kHz (see a symbol G101 in FIG. 7A).In the transmission characteristic shown in FIG. 7B, both an S parameterS21 for transmission efficiency between the feed unit 1 and theelectronic unit 102A (light load) and an S parameter S31 fortransmission efficiency between the feed unit 1 and the electronic unit102B (heavy load) abruptly decrease at a frequency in the vicinity ofthe resonance frequency f_(res) of 120 kHz (see a symbol G102 in FIG.7B). In particular, the value of the S parameter S31 on a heavy loadside remarkably decreases at the frequency in the vicinity of theresonance frequency f_(res) of 120 kHz.

It is to be noted that the transmission characteristics shown in FIGS.7A and 7B are also obtained by simulation under an example condition ofZ1=10Ω, Z2=300Ω, Z3=10Ω, L1=393 μH, C1=4.5 nF, L2=2.5 μH, and C2=703 nF.

Such an abrupt degradation in the transmission characteristics (inparticular, on the heavy load side) at the frequency in the vicinity ofthe resonance frequency f_(res) is caused by large impedance mismatchdue to an effect (interaction) between the LC resonant circuits (the LCparallel resonant circuits in the power receiving sections 100) in theplurality of feeding target units. Such a condition that one of theplurality of feeding target units is loaded lightly while the other isloaded heavily may occur in practice, for example, in an approximatelyfully charged state of a battery in one feeding target unit, in a stateof one feeding target unit performing communication, and in a state ofthe plurality of feeding target units being charged in a time-divisionmanner.

Thus, the configuration of the power receiving section 100 in each ofthe comparative examples 1-1 and 1-2 hardly improves the transmissioncharacteristics, for example, in the case of charge of the plurality offeeding target units (1:N charge).

Comparative Example 2-1

FIG. 8 then illustrates a circuit configuration of each of a feedsection (power transmission section) 110 and a power receiving section200 in a feed system (a feed system 204A) according to a comparativeexample 2-1. In the comparative example 2-1, the feed system 204Aincludes one feed unit 1 having a power transmission section 110, andtwo electronic units 202A and 202B each having a power receiving section200. The electronic units 202A and 202B each have a configurationsimilar to that of the electronic units 2A and 2B in the embodimentexcept that the power receiving section 200 is provided in place of thepower receiving section 210.

The power receiving section 200 includes a power receiving coil L2 and acapacitor C2 as a resonance capacitor. The power receiving coil L2 andthe capacitor C2 are connected in series to each other and thus definean LC series resonant circuit. Specifically, the power receiving section200 is different in a configuration from the power receiving section 210in that the capacitor C2 is provided in place of the capacitor C2 s, andthe capacitor C2 p is not provided (is omitted).

The feed system 204A including the power receiving section 200 havingsuch a configuration shows transmission characteristics, for example, asshown in FIG. 9 during power transmission with a magnetic field as shownby arrows P201 a and P201 b in FIG. 8, for example. Specifically, bothan S parameter S21 for transmission efficiency between the feed unit 1and the electronic unit 202A (light load) and an S parameter S31 fortransmission efficiency between the feed unit 1 and the electronic unit202B (heavy load) generally decrease, namely, decrease over thesubstantially all frequency ranges (see broken-line arrows in FIG. 9).This is because the LC series resonant circuit is formed in the powerreceiving section 200 and impedance is reduced thereby. It is to benoted that the transmission characteristics shown in FIG. 9 are alsoobtained by simulation with values of the parameters being the same asthose in the comparative example 1-2.

In this way, although the configuration of the power receiving section200 in the comparative example 2-1 does not cause the abrupt degradationin the transmission characteristics in the vicinity of the resonancefrequency f_(res) during charge of a plurality of feeding target unitsunlike in the comparative example 1-2, the configuration still hardlyachieves an improvement in the transmission characteristics includingtransmission efficiency.

Comparative Example 2-2

FIG. 10 illustrates a feed system (a feed system 204B) according to acomparative example 2-2, which is similar to the feed system 204A in thecomparative example 2-1 except that two electronic units 202C and 202Dare provided in place of the two electronic units 202A and 202B. Theelectronic units 202C and 202D have a configuration similar to that ofthe electronic units 202A and 202B, respectively, except that atransformer including a pair of coils L201 and L202 is further providedbetween the power receiving section 200 and a block of an impedance Z2or Z3.

The feed system 204B further including the transformer having such aconfiguration shows transmission characteristics, for example, as shownin FIG. 11 during power transmission with a magnetic field as shown byarrows P202 a and P202 b in FIG. 10, for example. Specifically, areduction in transmission efficiency does not occur unlike in thecomparative examples 1-2 and 2-1, and both an S parameter S21 (lightload) and an S parameter S31 (heavy load) are maximized at a frequencyin the vicinity of the resonance frequency f_(res) of 120 kHz. It is tobe noted that the transmission characteristics shown in FIG. 11 are alsoobtained by simulation with values of the parameters being the same asthose in the comparative examples 1-2 and 2-1.

In the comparative example 2-2, however, the electronic units 202C and202D each have the transformer, including a pair of coils L201 and L202,that transforms a reduced load impedance to improve the transmissionefficiency. Specifically, the number of components necessarily increaseswithin a feeding target unit, making it difficult to improve thetransmission efficiency in a simple configuration though size and costare reduced. In addition, while an ideal transformer having no loss isused in the simulation, an actual transformer contains a resistancecomponent causing loss, leading to a possibility of degradation intransmission efficiency.

Thus, the feeding target units, such as electronic units, in thecomparative examples 1-1, 1-2, 2-1, and 2-2 hardly achieve animprovement in the transmission characteristics in a simpleconfiguration during power transmission with a magnetic field(noncontact feeding).

Embodiment

In contrast, as shown in the embodiment of FIG. 3, the electronic units2A and 2B in the embodiment each include the power receiving section 210in which the power receiving coil L2 and the capacitor C2 p areconnected in parallel to each other and thus define the parallel circuit(the LC parallel resonant circuit). In addition, the capacitor C2 s isconnected in series to the LC parallel resonant circuit. Specifically,the power receiving coil L2 in the LC parallel resonant circuit and thecapacitor C2 s define the LC series resonant circuit.

As a result, the two LC resonant circuits (the LC parallel resonantcircuit and the LC series resonant circuit) perform LC resonanceoperations at the resonance frequency, f_(res), which is substantiallythe same as or close to the frequency of the high-frequency powergenerated by the high-frequency power generation circuit 111.Specifically, during power transmission with a magnetic field, the LCparallel resonant circuit performs an LC parallel resonance operation,and the power receiving coil L2 in the LC parallel resonant circuit andthe capacitor C2 s perform an LC series resonance operation. Tocollectively express the two LC resonance operations (the LC parallelresonance operation and the LC series resonance operation) of the powerreceiving section 210, the resonance frequency f_(res) is defined by thefollowing expression (1).

$\begin{matrix}{\mspace{14mu} \left\lbrack {{Expression}\mspace{14mu} 1} \right\rbrack } & \; \\{{L\; 2 \times \left( {{C\; 2p} + {C\; 2s}} \right)} = \frac{1}{\left( {2\pi \; f_{res}} \right)^{2}}} & (1)\end{matrix}$

Consequently, for example, the embodiment shows transmissioncharacteristics of Example 1 as shown in FIGS. 12A and 12B during powertransmission with a magnetic field. Specifically, even if a differencein a load is large between a plurality of feeding target units, forexample, even if one electronic unit 2A has an impedance Z2 of 300Ω(light load), and the other electronic unit 2B has an impedance Z3 of10Ω (heavy load), the following transmission characteristics are shown.That is, as shown in FIG. 12A, the characteristics of the inputimpedance Zin1 does not significantly vary in the vicinity of theresonance frequency f_(res) compared with a case of one feeding targetunit. Moreover, as shown in FIG. 12B, a reduction in transmissionefficiency does not occur as it does in the comparative examples 1-2 and2-1, and both an S parameter S21 (light load) and an S parameter S31(heavy load) are maximized at a frequency in the vicinity of theresonance frequency f_(res) of 120 kHz. In addition, power ispreferentially (more) distributed to a unit (the electronic unit 2B) ona heavy load side that needs to be supplied with relatively much power.It is to be noted that the transmission characteristics shown in FIGS.12A and 12B are also obtained by simulation under an example conditionof Z1=10Ω, Z2=300Ω, Z3=10Ω, L1=393 μH, C1=4.5 nF, L2=14 μH, C2 p=55 nF,and C2 s=70 nF.

Moreover, in the embodiment, each of the electronic units 2A and 2B doesnot need the transformer unlike in the comparative example 2-2, and thusthe number of components need not be increased within a feeding targetunit, and consequently transmission efficiency is improved in a simpleconfiguration, while size and cost are reduced.

As described above, in the embodiment, the power receiving coil L2 andthe capacitor C2 p are connected in parallel to each other and thusdefine the parallel circuit (the LC parallel resonant circuit), and thecapacitor C2 s is connected in series to the LC parallel resonantcircuit, resulting in the LC series resonance operation in addition tothe LC parallel resonance operation of the LC parallel resonant circuitduring power transmission with a magnetic field. Consequently, forexample, even if power is transmitted to a plurality of feeding targetunits, such as electronic units, transmission characteristics includingtransmission efficiency are improved without increasing components suchas a transformer and a balun. As a result, transmission characteristicsare improved in a simple configuration during power transmission with amagnetic field.

In addition, a real-part impedance of each of the electronic units 2Aand 2B is adjusted through varying a ratio between capacitance values ofthe capacitors C2 p and C2 s in the power receiving section 210, andthus the real-part impedance is appropriately adjusted in accordancewith any primary impedance.

Furthermore, in the embodiment, compared to a second embodimentdescribed below using an inductive reactance element such as a coil L2s, a capacitive reactance element (the capacitor C2 s) is used as areactance element connected in series to the LC parallel resonantcircuit, leading to the following effects. Specifically, the capacitivereactance element typically has a higher Q value than that of theinductive reactance element, leading to a further improvement intransmission efficiency. In addition, the capacitive reactance element(such as a capacitor) is typically smaller in size than the inductivereactance element (such as a coil), leading to a reduction in size ofthe unit.

Other embodiments (second to fourth embodiments) of the disclosure arenow described. It is to be noted that the same components as those inthe first embodiment are designated by the same symbols, and descriptionthereof is appropriately omitted.

Second Embodiment Configuration of Feed System 4

FIG. 13 illustrates a circuit configuration of each of a powertransmission section 110 and a power receiving section 210 of a feedsystem (feed system 4A) according to a second embodiment. The feedsystem 4A of the embodiment includes one feed unit 1 having a powertransmission section 110, and two electronic units 2A and 2B each havinga power receiving section 210A. In the embodiment, the electronic units2A and 2B each have a configuration similar to that of the electronicunits 2A and 2B in the first embodiment except that the power receivingsection 210A is provided in place of the power receiving section 210.

(Power Receiving Section 210A)

The power receiving section 210A includes a power receiving coil L2 preceiving power (from magnetic fluxes) transmitted from the powertransmission section 110, a capacitor C2 that together with the powerreceiving coil L2 p define an LC resonant circuit (LC parallel resonantcircuit), and a coil L2 s as an inductive reactance element (inductiveelement). The capacitor C2 is electrically connected in parallel to thepower receiving coil L2 p, and the coil L2 s is electrically connectedin series to the capacitor C2, or to the LC parallel resonant circuit.Specifically, a first end of the capacitor C2 is connected to a firstend of the power receiving coil L2 and a first end of the coil L2 s, anda second end of the coil L2 s is connected to a first end of a block ofan impedance Z2 or Z3. Second ends of the power receiving coil L2, thecapacitor C2, and the blocks of the impedance Z2 and the impedance Z3are grounded.

In the second embodiment, the power receiving coil L2 p and thecapacitor C2 define the LC parallel resonant circuit, and the capacitorC2 in the LC parallel resonant circuit and the coil L2 s define an LCresonant circuit (an LC series resonant circuit). In addition, these twoLC resonant circuits (the LC parallel resonant circuit and the LC seriesresonant circuit) perform LC resonance operations at the resonancefrequency, f_(res), which is substantially the same as or close to thefrequency of the high-frequency power (AC signal) generated by thehigh-frequency power generation circuit 111. Specifically, the LCresonant circuit (the LC series resonant circuit) defined by the powertransmission coil L1 and the capacitor C1 in the power transmissionsection 110 and the LC resonant circuits defined by the power receivingcoil L2 p, the coil L2 s, and the capacitor C2 in the power receivingsection 210 perform

[Function and Effect of Feed System 4A]

As described above, in the embodiment, the electronic units 2A and 2Beach include the power receiving section 210A in which the powerreceiving coil L2 p and the capacitor C2 are connected in parallel toeach other and thus define the parallel circuit (the LC parallelresonant circuit). In addition, the coil L2 s is connected in series tothe LC parallel resonant circuit. Specifically, the capacitor C2 in theLC parallel resonant circuit and the coil L2 s define the LC seriesresonant circuit.

Consequently, the two LC resonant circuits (the LC parallel resonantcircuit and the LC series resonant circuit) perform LC resonanceoperations at the resonance frequency f_(res) during power transmissionas shown by arrows P2 a and P2 b in FIG. 13, for example. Specifically,during power transmission with a magnetic field, the LC parallelresonant circuit performs an LC parallel resonance operation, and thecapacitor C2 in the LC parallel resonant circuit and the coil L2 sperform an LC series resonance operation. To collectively express thetwo LC resonance operations (the LC parallel resonance operation and theLC series resonance operation) of the power receiving section 210A, theresonance frequency f_(res) is defined by the following expression (2).

$\begin{matrix}{\left\lbrack {{Expression}\mspace{14mu} 2} \right\rbrack \mspace{166mu}} & \; \\{{C\; 2 \times \frac{L\; 2p \times L\; 2s}{\left( {{L\; 2p} + {L\; 2s}} \right)}} = \frac{1}{\left( {2\pi \; f_{res}} \right)^{2}}} & (2)\end{matrix}$

As a result, for example, the embodiment shows transmissioncharacteristics of Example 2 as shown in FIG. 14 during powertransmission with a magnetic field. Specifically, even if a differencein a load is large between a plurality of feeding target units, forexample, even if one electronic unit 2A has an impedance Z2 of 300Ω(light load), and the other electronic unit 2B has an impedance Z3 of10Ω (heavy load), transmission characteristics similar to those in theExample 1 are shown. That is, a reduction in transmission efficiencydoes not occur as it does in the comparative examples 1-2 and 2-1, andboth an S parameter S21 (light load) and an S parameter S31 (heavy load)are maximized at a frequency in the vicinity of the resonance frequencyf_(res) of 120 kHz. In addition, power is preferentially (more)distributed to a unit (the electronic unit 2B) on a heavy load side thatneeds to be supplied with relatively much power. It is to be noted thatthe transmission characteristics shown in FIG. 14 are also obtained bysimulation under an example condition of Z1=10Ω, Z2=300Ω, Z3=10Ω, L1=393μH, C1=4.5 nF, L2 p=69 μH, C2=55 nF, and C2 s=55 nF.

Moreover, in the embodiment, each of the electronic units 2A and 2B alsodoes not need the transformer, which is unlike the comparative example2-2, and thus the number of components need not be increased within afeeding target unit, and consequently transmission efficiency isimproved in a simple configuration, while size and cost are reduced.

As described above, the second embodiment also provides the effectssimilar to those in the first embodiment through the similar functions.Specifically, transmission characteristics are improved in a simpleconfiguration during power transmission with a magnetic field.

Third Embodiment Configuration of Power Transmission Sections 110A and110B

FIGS. 15A and 15B illustrate circuit configurations of powertransmission sections 110A and 110B, respectively, according to a thirdembodiment. The feed system of the embodiment includes one feed unit 1having a power transmission section 110A or 110B, and one or morefeeding target units (electronic units). In the embodiment, the feedunit 1 has a configuration similar to that of the feed unit 1 in thefirst and second embodiments except that the power transmission section110A or 110B is provided in place of the power transmission section 110.

(Power Transmission Section 110A)

The power transmission section 110A shown in FIG. 15A includes a powertransmission coil L1, a capacitor C1 p that together with the powertransmission coil L1 defines an LC resonant circuit (an LC parallelresonant circuit), and a capacitor C1 s as a capacitive reactanceelement (capacitive element). The capacitor C1 p is electricallyconnected in parallel to the power transmission coil L1, and thecapacitor C1 s is electrically connected in series to the powertransmission coil L1, or to the LC parallel resonant circuit.Specifically, a first end of the capacitor C1 p is connected to a firstend of the power transmission coil L1 and a first end of the capacitorC1 s, and a second end of the capacitor C1 s is connected to a first endof a block of an impedance Z1. Second ends of the power transmissioncoil L1, the capacitor C1 p, and the block of the impedance Z1 aregrounded.

In the power transmission section 110A, the power transmission coil L1and the capacitor C1 p define the LC parallel resonant circuit, and thepower transmission coil L1 in the LC parallel resonant circuit and thecapacitor C1 s define an LC resonant circuit (an LC series resonantcircuit). The two LC resonant circuits (the LC parallel resonant circuitand the LC series resonant circuit) perform LC resonance operations at aresonance frequency, f_(res), which is substantially the same as orclose to the frequency of the high-frequency power (AC signal) generatedby a high-frequency power generation circuit 111. Specifically, the LCresonant circuit defined by the power transmission coil L1 and thecapacitor C1 p or C1 s, and an LC resonant circuit in the feeding targetunit perform LC resonance operations at substantially the same resonancefrequency f_(res).

(Power Transmission Section 110B)

The power transmission section 110B shown in FIG. 15B includes a powertransmission coil L1 p, a capacitor C1 that together with the powertransmission coil L1 p define an LC resonant circuit (an LC parallelresonant circuit), and a coil L1 s as an inductive reactance element(inductive element). The capacitor C1 is electrically connected inparallel to the power transmission coil L1 p, and the coil L1 s iselectrically connected in series to the capacitor C1, or to the LCparallel resonant circuit. Specifically, a first end of the capacitor C1is connected to a first end of the power transmission coil L1 p and afirst end of the coil L1 s, and a second end of the coil L1 s isconnected to a first end of a block of an impedance Z1. Second ends ofthe power transmission coil L1 p, the capacitor C1, and the block of theimpedance Z1 are grounded.

In the power transmission section 110B, the power transmission coil L1 pand the capacitor C1 define the LC parallel resonant circuit, and thecapacitor C1 in the LC parallel resonant circuit and the coil L1 sdefine an LC resonant circuit (an LC series resonant circuit). The twoLC resonant circuits (the LC parallel resonant circuit and the LC seriesresonant circuit) perform LC resonance operations at a resonancefrequency, f_(res), which is substantially the same as or close to thefrequency of the high-frequency power (AC signal) generated by thehigh-frequency power generation circuit 111. Specifically, the LCresonant circuit defined by the capacitor C1 and the power transmissioncoil L1 p or the coil L1 s, and the LC resonant circuit in the feedingtarget unit perform LC resonance operations at substantially the sameresonance frequency f_(res).

[Function and Effect of Power Transmission Sections 110A and 110B]

As described above, in the third embodiment, the feed unit 1 includesthe power transmission section 110A in which the power transmission coilL1 and the capacitor C1 p are connected in parallel to each other andthus define the LC parallel resonant circuit. In addition, the capacitorC1 s is connected in series to the LC parallel resonant circuit.Specifically, the coil L1 in the LC parallel resonant circuit and thecapacitor C1 s define the LC series resonant circuit.

Consequently, the two LC resonant circuits (the LC parallel resonantcircuit and the LC series resonant circuit) perform LC resonanceoperations at the resonance frequency f_(res). Specifically, duringpower transmission with a magnetic field, the LC parallel resonantcircuit performs an LC parallel resonance operation, and the coil L1 inthe LC parallel resonant circuit and the capacitor C1 s perform an LCseries resonance operation. To collectively express the two LC resonanceoperations (the LC parallel resonance operation and the LC seriesresonance operation) of the power transmission section 110A, theresonance frequency f_(res) is defined by an expression (3) describedbelow.

As described above, in the third embodiment, alternatively, the feedunit 1 includes the power transmission section 110B in which the powertransmission coil L1 p and the capacitor C1 are connected in parallel toeach other and thus define the LC parallel resonant circuit. Inaddition, the coil L1 s is connected in series to the LC parallelresonant circuit. Specifically, the capacitor C1 in the LC parallelresonant circuit and the coil L1 s define the LC series resonantcircuit.

Consequently, the two LC resonant circuits (the LC parallel resonantcircuit and the LC series resonant circuit) perform LC resonanceoperations at the resonance frequency f_(res). Specifically, duringpower transmission with a magnetic field, the LC parallel resonantcircuit performs an LC parallel resonance operation, and the capacitorC1 in the LC parallel resonant circuit and the coil L1 s perform an LCseries resonance operation. To collectively express the two LC resonanceoperations (the LC parallel resonance operation and the LC seriesresonance operation) of the power transmission section 110B, theresonance frequency f_(res) is defined by the following expression (4).

$\begin{matrix}{\left\lbrack {{Expression}\mspace{14mu} 3} \right\rbrack \mspace{175mu}} & \; \\\left\{ \begin{matrix}{{L\; 1 \times \left( {{C\; 1p} + {C\; 1s}} \right)} = \frac{1}{\left( {2\pi \; f_{res}} \right)^{2}}} \\{{C\; 1 \times \frac{L\; 1p \times L\; 1s}{\left( {{L\; 1p} + {L\; 1\; s}} \right)}} = \frac{1}{\left( {2\pi \; f_{res}} \right)^{2}}}\end{matrix} \right. & \begin{matrix}(3) \\(4)\end{matrix}\end{matrix}$

Moreover, in the third embodiment, the feed unit 1 also does not needthe transformer, which is unlike the comparative example 2-2, and thusthe number of components need not be increased within the feed unit 1,and consequently transmission efficiency is improved in a simpleconfiguration, while size and cost are reduced.

As described above, the embodiment also provides the effects similar tothose in the first and second embodiments through the similar functions.Specifically, transmission characteristics are improved in a simpleconfiguration during power transmission with a magnetic field.

Fourth Embodiment

FIG. 16 illustrates a circuit configuration of each of a powertransmission section 110A or 110B and a power receiving section 210 or210A of a feed system (a feed system 4B) according to a fourthembodiment. The feed system 4B of the fourth embodiment includes onefeed unit 1 having the power transmission section 110A or 110B, and twoelectronic units 2A and 2B each having the power receiving section 210or 210A.

Specifically, the feed system 4B corresponds to a combination of thefeed unit 1 having the power transmission section 110A or 110B describedin the third embodiment and the electronic units 2A and 2B having thepower receiving section 210 or 210A described in the first or secondembodiment. That is, in one or both of the power transmission section inthe feed unit 1 and the power receiving section in each of theelectronic units 2A and 2B, a power transmission coil or a powerreceiving coil and a resonance capacitor (a first or second capacitor)are connected in parallel to each other, and thus define an LC parallelresonant circuit. In addition, a capacitive or inductive reactanceelement is in series connection to the LC parallel resonant circuit.

The embodiment having such a configuration also provides the effectssimilar to those in the first to third embodiments through the similarfunctions. Specifically, transmission characteristics are improved in asimple configuration during power transmission with a magnetic field.

In particular, in the case where the LC series resonant circuit isprovided in both the power transmission section and the power receivingsection (in the case where both the power transmission section 110 or110B and the power receiving section 210 or 210A are provided), thefollowing effect is also obtained. Specifically, the number ofparameters for impedance matching is increased, and thus impedancematching is readily achieved.

[Modifications]

While the technology of the disclosure has been described with severalforegoing embodiments, the technology is not limited to thoseembodiments, and various modifications or alterations of the technologymay be made.

For example, each of the various types of coils (a power transmissioncoil, a power receiving coil, and a coil used as an inductive reactanceelement) described in the foregoing embodiments may have a variety ofconfigurations/shapes, without limitation. Specifically, the coil mayhave, for example, a spiral or loop shape, a bar shape including amagnetic substance, an alpha winding shape where a spiral coil is set intwo layers in a folded manner, a spiral shape in three or more layers,and a helical shape where a wire is wound in a thickness direction. Thecoil is not limited to a winding coil including a conductive wire rod,and may be a conductive patterned coil formed of a printed circuit boardor a flexible printed circuit board. It is to be noted that a couplingcoefficient between the power transmission coil and the power receivingcoil is desirably 0.001 or more in each case.

Moreover, while the foregoing embodiments have been described with anelectronic unit as an example of a feeding target unit, other feedingtarget units (for example, vehicles such as an electric car) may be usedwithout limitation.

Furthermore, while the foregoing embodiments have been specificallydescribed with the components of the feed unit and of the electronicunit, each of the units may not have all of the components, or mayfurther have other components. For example, the feed unit or theelectronic unit may have a communication function or some controlfunction, a display function, a function of verifying a secondary unit,a function of determining a secondary unit placed on a primary unit, anda function of detecting mixing of dissimilar metals.

In addition, while the foregoing embodiments have been mainly describedwith an example case where a plurality of electronic units (namely, twoelectronic units) are provided in the feed system, only one electronicunit may be provided in the feed system without limitation.

In addition, while the embodiments have been described with the chargingtray as an example of a feed unit, for a small electronic unit (CE unit)such as a mobile phone, the feed unit is not limited to such a householdcharging tray, and may be applied to any other chargers for variouselectronic units. In addition, the feed unit is not necessarily of atray-type, and may be of a stand-type for an electronic unit, such as aso-called cradle.

It is possible to achieve at least the following configurations from theabove-described example embodiments and the modifications of thedisclosure.

(1) A power receiving circuit, including:

an LC parallel resonant circuit; and

a reactance element electrically connected in series to the LC parallelresonant circuit,

wherein,

-   -   the power receiving circuit receives power in a noncontact        manner.

(2) The power receiving circuit of (1), wherein the reactance element isa capacitive element.

(3) The power receiving circuit of (1), wherein the reactance element isan inductive element.

(4) The power receiving circuit of (1), wherein one of a coil and acapacitor in the LC parallel resonant circuit and the reactance elementdefine an LC series resonant circuit.

(5) The power receiving circuit of (1), wherein the power receivingcircuit receives power in the noncontact manner via a coil in the LCparallel resonant circuit.

(6) The power receiving circuit of (1), wherein power is transmitted tothe power receiving circuit with a magnetic field.

(7) A power transmitting circuit, including:

an LC parallel resonant circuit; and

a reactance element electrically connected in series to the LC parallelresonant circuit,

wherein,

-   -   the power transmitting circuit transmits power in a noncontact        manner.

(8) The power transmitting circuit of (7), wherein the reactance elementis a capacitive element.

(9) The power transmitting circuit of (7), wherein the reactance elementis an inductive element.

(10) The power transmitting circuit of (7), wherein one of a coil and acapacitor in the LC parallel resonant circuit and the reactance elementdefine an LC series resonant circuit.

(11) The power transmitting circuit of (7), wherein the powertransmitting circuit transmits power in the noncontact manner via a coilin the LC parallel resonant circuit.

(12) The power transmitting circuit of (7), wherein the powertransmitting circuit transmits power with a magnetic field.

(13) An apparatus including:

a power receiving section, the power receiving section including

-   -   (a) an LC parallel resonant circuit, and    -   (b) a reactance element electrically connected in series to the        LC parallel resonant circuit,

wherein,

-   -   the power receiving section receives power in a noncontact        manner.

(14) The apparatus of (13), wherein the reactance element is acapacitive element.

(15) The apparatus of (13), wherein the reactance element is aninductive element.

(16) The apparatus of (13), wherein one of a coil and a capacitor in theLC parallel resonant circuit and the reactance element define an LCseries resonant circuit.

(17) The apparatus of (13), further including:

a battery that is chargeable using power received by the power receivingsection.

(18) The apparatus of (13), wherein the apparatus is an electronic unitor a vehicle.

(19) The apparatus of (18), wherein the electronic unit is a mobile orportable device.

(20) The apparatus of (18), wherein the vehicle is an electric car.

(21) The apparatus of (14), wherein a ratio between capacitance valuesof a capacitor in the LC parallel resonant circuit and the reactanceelement can be varied.

(22) The apparatus of (13), wherein the power receiving section receivesAC power, and the apparatus further includes:

a rectifier circuit that rectifies AC power supplied from the powerreceiving section to generate DC power.

(23) The apparatus of (13), further including:

a load including a battery that is chargeable using power received bythe power receiving section.

(24) The apparatus of (13), wherein the power receiving section receivespower in the noncontact manner via a coil in the LC parallel resonantcircuit.

(25) The apparatus of (13), wherein power is transmitted to theapparatus with a magnetic field.

(26) The apparatus of (21), further including:

a voltage stabilization circuit that performs voltage stabilizationoperation based on the DC power supplied from the rectifier circuit forcharging a battery.

(27) A feed system including:

a feed unit; and

one or more target units receiving power transmitted by the feed unit,

wherein,

-   -   each of the one or more target units includes a power receiving        section, the power receiving section including        -   (a) an LC parallel resonant circuit, and        -   (b) a reactance element electrically connected in series to            the LC parallel resonant circuit,    -   the power receiving section receiving power from the feed unit        in a noncontact manner.

(28) The feed system of (26), wherein:

the reactance element is a capacitive or inductive element, and

one of a coil and a capacitor in the LC parallel resonant circuit andthe reactance element define an LC series resonant circuit.

(29) The feed system of (26), wherein:

the reactance element is a capacitive element, and

a ratio between capacitance values of a capacitor in the LC parallelresonant circuit and the reactance element can be varied.

(30) A feed system including:

a feed unit; and

one or more target units receiving power transmitted by the feed unit,

wherein,

-   -   the feed unit includes a power transmission section, the power        transmission section including        -   (a) an LC parallel resonant circuit, and        -   (b) a reactance element electrically connected in series to            the LC parallel resonant circuit,        -   the power transmission section transmitting power to each of            the one or more target units in a noncontact manner.

(31) The feed system of (30), wherein:

the reactance element is a capacitive or inductive element, and

one of a coil and a capacitor in the LC parallel resonant circuit andthe reactance element define an LC series resonant circuit.

(32) A feed system including:

a feed unit; and

one or more target units receiving power transmitted by the feed unit,

wherein,

-   -   each of the one or more target units includes a power receiving        section, the power receiving section including        -   (a) a first LC parallel resonant circuit, and        -   (b) a first reactance element electrically connected in            series to the LC parallel resonant circuit,    -   the power receiving section receiving power from the feed unit        in a noncontact manner.

(33) The feed system of (32), wherein:

the first reactance element is a capacitive or inductive element, and

one of a coil and a capacitor in the first LC parallel resonant circuitand the first reactance element define a first LC series resonantcircuit.

(34) The feed system of (32), wherein:

the first reactance element is a capacitive element, and

a ratio between capacitance values of a capacitor in the first LCparallel resonant circuit and the first reactance element can be varied.

(35) The feed system of (32), wherein the feed unit transmits power tothe one or more target units with a magnetic field, and the powerreceiving section receives the transmitted power in the noncontactmanner via a coil in the first LC parallel resonant circuit.

(36) The feed system of (32), wherein the feed unit includes a powertransmission section, the power transmission section including a coiland a capacitor that are electrically connected in series to form an LCseries resonant circuit.

(37) The feed system of (32), wherein the feed unit includes a powertransmission section, the power transmission section including

(a) a second LC parallel resonant circuit, and

(b) a second reactance element electrically connected in series to thesecond LC parallel resonant circuit.

(38) The feed system of (32), wherein:

the second reactance element is a capacitive or inductive element, and

one of a coil and a capacitor in the second LC parallel resonant circuitand the second reactance element define a second LC series resonantcircuit.

(39) The feed system of (32), wherein each of the one or more targetunits is one of an electronic unit and a vehicle.

(40) The feed system of (39), wherein the electronic unit is a mobile orportable device.

(41) The feed system of (39), wherein the vehicle is an electric car.

(42) A feed system including:

a feed unit; and

one or more target units receiving power transmitted by the feed unit,

wherein,

-   -   the feed unit includes a power transmission section, the power        transmission section including    -   (a) a first LC parallel resonant circuit, and    -   (b) a first reactance element electrically connected in series        to the first LC parallel resonant circuit,        -   the power transmission section transmitting power to each of            the one or more target units in a noncontact manner.

(43) The feed system of (42), wherein:

the first reactance element is a capacitive or inductive element, and

one of a coil and a capacitor in the first LC parallel resonant circuitand the reactance element define a first LC series resonant circuit.

(44) The feed system of (42), wherein each of the one or more targetunits includes a power receiving section, the power receiving sectionincluding

(a) a second LC parallel resonant circuit, and

(b) a second reactance element electrically connected in series to thesecond LC parallel resonant circuit.

(45) The feed system of (42), wherein:

the second reactance element is a capacitive or inductive element, and

one of a coil and a capacitor in the second LC parallel resonant circuitand the second reactance element define a second LC series resonantcircuit.

(46) The feed system of (42), wherein each of the one or more targetunits is one of an electronic unit and a vehicle.

(47) The feed system of (46), wherein the electronic unit is a mobile orportable device.

(48) The feed system of (46), wherein the vehicle is an electric car.

(49) The feed system of (42), wherein the power transmission sectiontransmits power to each of the one or more target units in thenoncontact manner via a coil in the first LC parallel resonant circuit.

The present disclosure contains subject matter related to that disclosedin Japanese Priority Patent Application JP 2011-193543 filed in theJapan Patent Office on Sep. 6, 2011, the entire content of which ishereby incorporated by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A power receiving circuit, comprising: an LC parallel resonantcircuit; and a reactance element electrically connected in series to theLC parallel resonant circuit, wherein, the power receiving circuitreceives power in a noncontact manner.
 2. The power receiving circuit ofclaim 1, wherein the reactance element is a capacitive element.
 3. Thepower receiving circuit of claim 1, wherein the reactance element is aninductive element.
 4. The power receiving circuit of claim 1, whereinone of a coil and a capacitor in the LC parallel resonant circuit andthe reactance element define an LC series resonant circuit.
 5. A powertransmitting circuit, comprising: an LC parallel resonant circuit; and areactance element electrically connected in series to the LC parallelresonant circuit, wherein, the power transmitting circuit transmitspower in a noncontact manner.
 6. The power transmitting circuit of claim5, wherein the reactance element is a capacitive element.
 7. The powertransmitting circuit of claim 5, wherein the reactance element is aninductive element.
 8. The power transmitting circuit of claim 5, whereinone of a coil and a capacitor in the LC parallel resonant circuit andthe reactance element define an LC series resonant circuit.
 9. Anapparatus comprising: a power receiving section, the power receivingsection including (a) an LC parallel resonant circuit, and (b) areactance element electrically connected in series to the LC parallelresonant circuit, wherein, the power receiving section receives power ina noncontact manner.
 10. The apparatus of claim 9, wherein the reactanceelement is a capacitive element.
 11. The apparatus of claim 9, whereinthe reactance element is an inductive element.
 12. The apparatus ofclaim 9, wherein one of a coil and a capacitor in the LC parallelresonant circuit and the reactance element define an LC series resonantcircuit.
 13. The apparatus of claim 9, further comprising: a batterythat is chargeable using power received by the power receiving section.14. The apparatus of claim 9, wherein the apparatus is an electronicunit or a vehicle.
 15. The apparatus of claim 10, wherein a ratiobetween capacitance values of a capacitor in the LC parallel resonantcircuit and the reactance element can be varied.
 16. A feed systemcomprising: a feed unit; and one or more target units receiving powertransmitted by the feed unit, wherein, each of the one or more targetunits includes a power receiving section, the power receiving sectionincluding (a) an LC parallel resonant circuit, and (b) a reactanceelement electrically connected in series to the LC parallel resonantcircuit, the power receiving section receiving power from the feed unitin a noncontact manner.
 17. The feed system of claim 16, wherein: thereactance element is a capacitive or inductive element, and one of acoil and a capacitor in the LC parallel resonant circuit and thereactance element define an LC series resonant circuit.
 18. The feedsystem of claim 16, wherein: the reactance element is a capacitiveelement, and a ratio between capacitance values of a capacitor in the LCparallel resonant circuit and the reactance element can be varied.
 19. Afeed system comprising: a feed unit; and one or more target unitsreceiving power transmitted by the feed unit, wherein, the feed unitincludes a power transmission section, the power transmission sectionincluding (a) an LC parallel resonant circuit, and (b) a reactanceelement electrically connected in series to the LC parallel resonantcircuit, the power transmission section transmitting power to each ofthe one or more target units in a noncontact manner.
 20. The feed systemof claim 19, wherein: the reactance element is a capacitive or inductiveelement, and one of a coil and a capacitor in the LC parallel resonantcircuit and the reactance element define an LC series resonant circuit.